Turbomachine with alternatingly spaced turbine rotor blades

ABSTRACT

A turbomachine includes a turbine section including a turbine center frame and a turbine, the turbine including a plurality of low-speed turbine rotor blades and a plurality of high-speed turbine rotor blades alternatingly spaced along the axial direction. The plurality of low-speed turbine rotor blades each extend between a radially inner end and a radially outer end. At least two of the plurality of low-speed turbine rotor blades are spaced from one another along the axial direction and coupled to one another at the radially outer ends. The turbomachine also includes a gearbox aligned with, or positioned forward of, a midpoint of the turbine. The gearbox includes a first gear coupled to the plurality of low-speed turbine rotor blades, a second gear coupled to the plurality of high-speed turbine rotor blades, and a third gear coupled to the turbine center frame.

FIELD

The present subject matter relates generally to a turbomachine, and moreparticularly, to a turbine of a turbomachine having alternatingly spacedturbine rotor blades rotatable through a forward-positioned gearbox.

BACKGROUND

Gas turbine engines generally include a turbine section downstream of acombustion section that is rotatable with a compressor section to rotateand operate the gas turbine engine to generate power, such as propulsivethrust. General gas turbine engine design criteria often includeconflicting criteria that must be balanced or compromised, includingincreasing fuel efficiency, operational efficiency, and/or power outputwhile maintaining or reducing weight, part count, and/or packaging (i.e.axial and/or radial dimensions of the engine).

Within at least certain gas turbine engines, the turbine section mayinclude interdigitated rotors (i.e., successive rows or stages ofrotating airfoils or blades). For example, a turbine section may includea turbine having a first plurality of low speed turbine rotor blades anda second plurality of high speed turbine rotor blades. The firstplurality of low speed turbine rotor blades may be interdigitated withthe second plurality of high speed turbine rotor blades. Such aconfiguration may result in a more efficient turbine.

However, several problems may arise with such a configuration relatingto unwanted vibrations, clearance issues between the first and secondpluralities of rotor blades, etc. Accordingly, an improved turbine withinterdigitated turbine rotor blades would be useful.

BRIEF DESCRIPTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one exemplary embodiment of the present disclosure, a turbomachinedefining a radial direction and an axial direction is provided. Theturbomachine includes a turbine section including a turbine center frameand a turbine, the turbine defining a midpoint along the axial directionand including a plurality of low-speed turbine rotor blades and aplurality of high-speed turbine rotor blades, the plurality of low-speedturbine rotor blades and plurality of high-speed turbine rotor bladesalternatingly spaced along the axial direction, the plurality oflow-speed turbine rotor blades each extending between a radially innerend and a radially outer end, wherein at least two of the plurality oflow-speed turbine rotor blades are spaced from one another along theaxial direction and coupled to one another at the radially outer ends.The turbomachine also includes a gearbox aligned with, or positionedforward of, the midpoint of the turbine, the gearbox including a firstgear coupled to the plurality of low-speed turbine rotor blades, asecond gear coupled to the plurality of high-speed turbine rotor blades,and a third gear coupled to the turbine center frame.

In certain exemplary embodiments the gearbox is positioned forward ofthe midpoint of the turbine.

In certain exemplary embodiments the first gear of the gearbox is a ringgear, and wherein the second gear of the gearbox is a sun gear.

In certain exemplary embodiments each of the plurality of low-speedturbine rotor blades are coupled to one another at the radially outerends.

In certain exemplary embodiments the plurality of high-speed turbinerotor blades each extend between a radially inner end and a radiallyouter end, and wherein at least two of the plurality of high-speedturbine rotor blades are spaced from one another along the axialdirection and coupled to one another at the radially inner ends.

For example, in certain exemplary embodiments each of the plurality ofhigh-speed turbine rotor blades are coupled to one another at theradially inner ends.

In certain exemplary embodiments, the turbomachine further includes aturbine rear frame; and a spool, wherein plurality of low-speed turbinerotor blades is coupled to the first gear of the gearbox through thespool, wherein the spool is rotatably supported by a first bearing and asecond bearing, wherein the first bearing is positioned forward of thegearbox and supported by the turbine center frame, and wherein thesecond bearing is positioned aft of the gearbox and supported by theturbine rear frame.

In certain exemplary embodiments, the turbomachine further includes ahigh-speed support member, wherein the plurality of high-speed turbinerotor blades are coupled to the second gear through the high-speedsupport member.

For example, in certain exemplary embodiments the high-speed supportmember is rotatably supported by a bearing located aft of the gearbox.

For example, in certain exemplary embodiments the bearing is supportedby the turbine center frame.

For example, in certain exemplary embodiments the turbomachine furtherincludes a spool, wherein the plurality of low-speed turbine rotorblades is coupled to the first gear of the gearbox through the spool,and wherein the bearing is an inter-shaft bearing positioned between thespool and the high-speed support member.

For example, in certain exemplary embodiments the inter-shaft bearingsupports the spool at a radially inner side, and wherein the inner shaftbearing supports the high-speed support member at a radially outer side.

For example, in certain exemplary embodiments the high-speed supportmember is rotatably supported by a plurality of bearings located aft ofthe gearbox.

In certain exemplary embodiments the gearbox is aligned with, orpositioned aft of, the turbine center frame.

In certain exemplary embodiments the plurality of high-speed turbinerotor blades is coupled to the second gear of the gearbox through aflexible member. With such an exemplary embodiment, the turbomachine mayfurther include a spool, wherein plurality of low-speed turbine rotorblades is coupled to the first gear of the gearbox through the spool,and wherein the spool is connected to the first gear through a flexiblemember.

In another exemplary embodiment of the present disclosure, aturbomachine defining a radial direction and an axial direction isprovided. The turbomachine includes a spool; and a turbine sectionincluding a turbine center frame, a turbine rear frame, and a turbine,the turbine including a first plurality of turbine rotor blades and asecond plurality of turbine rotor blades, the first plurality of turbinerotor blades and second plurality of turbine rotor blades alternatinglyspaced along the axial direction, the turbine defining a midpoint alongthe axial direction. The turbomachine also includes a gearbox alignedwith, or positioned forward of, the midpoint of the turbine, the gearboxincluding a first gear coupled to the first plurality of rotor bladesthrough the spool, a second gear coupled to the second plurality ofrotor blades, and a third gear coupled to the turbine center frame. Theturbomachine also includes a bearing assembly including a bearingsupporting spool and located aft of the gearbox, the bearing supportedby the turbine rear frame.

In certain exemplary embodiments the gearbox is positioned forward ofthe midpoint of the turbine, and aligned with, or positioned aft of, theturbine center frame.

In certain exemplary embodiments the first plurality of turbine rotorblades is a plurality of low-speed turbine rotor blades, wherein thesecond plurality of turbine rotor blades is a plurality of high-speedturbine rotor blades.

For example, in certain exemplary embodiments the first gear of thegearbox is a ring gear, and wherein the second gear of the gearbox is asun gear.

For example, in certain exemplary embodiments the plurality of low-speedturbine rotor blades each extend between a radially inner end and aradially outer end, and wherein at least two of the plurality oflow-speed turbine rotor blades are spaced from one another along theaxial direction and coupled to one another at the radially outer ends.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a schematic cross sectional view of an exemplary gas turbineengine incorporating an exemplary embodiment of a turbine sectionaccording to an aspect of the present disclosure;

FIG. 2 is a close-up, schematic, cross sectional view of a turbinesection in accordance with yet another exemplary aspect of the presentdisclosure;

FIG. 3 is a close-up, schematic, cross sectional view of a turbinesection in accordance with still another exemplary aspect of the presentdisclosure; and

FIG. 4 is cross sectional view depicting exemplary blade pitch angles ofa turbine of a turbine section in accordance with an exemplaryembodiment of the present disclosure.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.

The terms “forward” and “aft” refer to relative positions within a gasturbine engine or vehicle, and refer to the normal operational attitudeof the gas turbine engine or vehicle. For example, with regard to a gasturbine engine, forward refers to a position closer to an engine inletand aft refers to a position closer to an engine nozzle or exhaust.

The terms “upstream” and “downstream” refer to the relative directionwith respect to fluid flow in a fluid pathway. For example, “upstream”refers to the direction from which the fluid flows, and “downstream”refers to the direction to which the fluid flows.

The terms “coupled,” “fixed,” “attached to,” and the like refer to bothdirect coupling, fixing, or attaching, as well as indirect coupling,fixing, or attaching through one or more intermediate components orfeatures, unless otherwise specified herein.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

The terms “low speed” and “high-speed” refer to relative speeds, such asrelative rotational speeds, of two components during operations of theturbomachine, and do not imply or require any minimum or maximumabsolute speeds.

Approximating language, as used herein throughout the specification andclaims, is applied to modify any quantitative representation that couldpermissibly vary without resulting in a change in the basic function towhich it is related. Accordingly, a value modified by a term or terms,such as “about”, “approximately”, and “substantially”, are not to belimited to the precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value, or the precision of the methods or machines forconstructing or manufacturing the components and/or systems. Forexample, the approximating language may refer to being within a 10percent margin.

Here and throughout the specification and claims, range limitations arecombined and interchanged, such ranges are identified and include allthe sub-ranges contained therein unless context or language indicatesotherwise. For example, all ranges disclosed herein are inclusive of theendpoints, and the endpoints are independently combinable with eachother.

The present disclosure is generally related to a turbomachine includinga turbine section having a turbine with a plurality of alternatinglyspaced turbine rotor blades. More specifically, the turbine includes afirst plurality of turbine rotor blades alternatingly spaced with, androtatable with (which, as used herein, refers to two components beingrotatable relative to one another), a second plurality of turbine rotorblades. More specifically, the first plurality of turbine rotor bladesare rotatable with the second plurality of turbine rotor blades througha gearbox. The gearbox is aligned with, or positioned forward of amidpoint of the turbine and includes a first gear coupled to the firstplurality of turbine rotor blades, a second gear coupled to the secondplurality of turbine rotor blades, and a third gear coupled to a turbineframe, such as a turbine center frame. Moreover, in at least certain ofthe embodiments described herein, the first plurality of turbine rotorblades may be coupled to a spool of the turbomachine, and theturbomachine may include a bearing assembly supporting such spool. Thebearing assembly may include a bearing located aft of the gearbox andsupported by a turbine rear frame.

Inclusion of the gearbox at a forward location relative to the midpointmay maintain the gearbox forward of a center of mass of the turbine,which may minimize vibrations of certain components, e.g., within theturbine section. Further, such may allow additional room for the bearingassembly to include one or more bearings positioned closer along anaxial direction to the center of mass of the turbine, with at least twoof such bearings straddling the midpoint of the turbine.

Referring now to the drawings, wherein identical numerals indicate thesame elements throughout the figures, FIG. 1 is a schematiccross-sectional view of a gas turbine engine in accordance with anexemplary embodiment of the present disclosure. More particularly, forthe embodiment of FIG. 1, the gas turbine engine is a high-bypassturbofan jet engine 10, referred to herein as “turbofan engine 10.” Asshown in FIG. 1, the turbofan engine 10 defines an axial direction A(extending parallel to a longitudinal centerline 12 provided forreference), a radial direction R, and a circumferential direction (i.e.,a direction extending about the axial direction A; not depicted). Ingeneral, the turbofan 10 includes a fan section 14 and a core turbineengine 16 disposed downstream from the fan section 14.

The exemplary core turbine engine 16 depicted generally includes asubstantially tubular outer casing 18 that defines an annular inlet 20.The outer casing 18 encases, in serial flow relationship, a compressorsection including a booster or low pressure (LP) compressor 22 and ahigh pressure (HP) compressor 24; a combustion section 26; a turbinesection including a high pressure (HP) turbine 28 and a low pressure(LP) turbine 30; and a jet exhaust nozzle section 32. The compressorsection, combustion section 26, and turbine section together define acore air flowpath 37 extending from the annular inlet 20 through the LPcompressor 22, HP compressor 24, combustion section 26, HP turbinesection 28, LP turbine section 30 and jet nozzle exhaust section 32. Ahigh pressure (HP) shaft or spool 34 drivingly connects the HP turbine28 to the HP compressor 24. A low pressure (LP) shaft or spool 36drivingly connects the LP turbine 30 to the LP compressor 22.

For the embodiment depicted, the fan section 14 includes a variablepitch fan 38 having a plurality of fan blades 40 coupled to a disk 42 ina spaced apart manner. As depicted, the fan blades 40 extend outwardlyfrom disk 42 generally along the radial direction R. Each fan blade 40is rotatable relative to the disk 42 about a pitch axis P by virtue ofthe fan blades 40 being operatively coupled to a suitable actuationmember 44 configured to collectively vary the pitch of the fan blades40, e.g., in unison. The fan blades 40, disk 42, and actuation member 44are together rotatable about the longitudinal axis 12 by LP shaft 36across a power gear box 46. The power gear box 46 includes a pluralityof gears for stepping down the rotational speed of the LP shaft 36 to amore efficient rotational fan speed.

Referring still to the exemplary embodiment of FIG. 1, the disk 42 iscovered by rotatable spinner cone 48 aerodynamically contoured topromote an airflow through the plurality of fan blades 40. Additionally,the exemplary fan section 14 includes an annular fan casing or outernacelle 50 that circumferentially surrounds the fan blades 40 of the fan38 and/or at least a portion of the core turbine engine 16. It should beappreciated that for the embodiment depicted, the nacelle 50 issupported relative to the core turbine engine 16 by a plurality ofcircumferentially-spaced outlet guide vanes 52. Moreover, a downstreamsection 54 of the nacelle 50 extends over an outer portion of the coreturbine engine 16 so as to define a bypass airflow passage 56therebetween.

During operation of the turbofan engine 10, a volume of air 58 entersthe turbofan 10 through an associated inlet 60 of the nacelle 50 and/orfan section 14. As the volume of air 58 passes across the fan blades 40,a first portion of the air 58 as indicated by arrows 62 is directed orrouted into the bypass airflow passage 56 and a second portion of theair 58 as indicated by arrow 64 is directed or routed into the LPcompressor 22. The ratio between the first portion of air 62 and thesecond portion of air 64 is commonly known as a bypass ratio. Thepressure of the second portion of air 64 is then increased as it isrouted through the high pressure (HP) compressor 24 and into thecombustion section 26, where it is mixed with fuel and burned to providecombustion gases 66.

The combustion gases 66 are routed through the HP turbine 28 where aportion of thermal and/or kinetic energy from the combustion gases 66 isextracted via sequential stages of HP turbine stator vanes 68 that arecoupled to an inner casing (not shown) and HP turbine rotor blades 70that are coupled to the HP shaft or spool 34, thus causing the HP shaftor spool 34 to rotate, thereby supporting operation of the HP compressor24. The combustion gases 66 are then routed through the LP turbine 30where a second portion of thermal and kinetic energy is extracted fromthe combustion gases 66 via sequential stages of a first plurality of LPturbine rotor blades 72 that are coupled to an outer drum 73, and asecond plurality of LP turbine rotor blades 74 that are coupled to aninner drum 75. The first plurality of LP turbine rotor blades 72 andsecond plurality of LP turbine rotor blades 74 are alternatingly spacedand rotatable with (i.e., relative to) one another through a gearbox(not shown) to together drive the LP shaft or spool 36, thus causing theLP shaft or spool 36 to rotate. Such system thereby supports operationof the LP compressor 22 and/or rotation of the fan 38.

The combustion gases 66 are subsequently routed through the jet exhaustnozzle section 32 of the core turbine engine 16 to provide propulsivethrust. Simultaneously, the pressure of the first portion of air 62 issubstantially increased as the first portion of air 62 is routed throughthe bypass airflow passage 56 before it is exhausted from a fan nozzleexhaust section 76 of the turbofan 10, also providing propulsive thrust.The HP turbine 28, the LP turbine 30, and the jet exhaust nozzle section32 at least partially define a hot gas path 78 for routing thecombustion gases 66 through the core turbine engine 16.

It should be appreciated, however, that the exemplary turbofan engine 10depicted in FIG. 1 is by way of example only, and that in otherexemplary embodiments, the turbofan engine 10 may have any othersuitable configuration. For example, in other exemplary embodiments, theturbine fan engine 10 may instead be configured as any other suitableturbomachine including, e.g., any other suitable number of shafts orspools, and excluding, e.g., the power gearbox 46 and/or fan 38, etc.Accordingly, it will be appreciated that in other exemplary embodiments,the turbofan engine 10 may instead be configured as, e.g., a turbojetengine, a turboshaft engine, a turboprop engine, etc., and further maybe configured as an aeroderivative gas turbine engine or industrial gasturbine engine.

Referring now to FIG. 2, a schematic, side, cross-sectional view isprovided of a turbine section 100 of a turbomachine in accordance withan exemplary embodiment of the present disclosure. The exemplary turbinesection 100 depicted in FIG. 2 may be incorporated into, e.g., theexemplary turbofan engine 10 described above with reference to FIG. 1.However, in other exemplary embodiments, the turbine section 100 may beintegrated into any other suitable machine utilizing a turbine.

Accordingly, it will be appreciated that the turbomachine generallydefines a radial direction R, an axial direction A, and a longitudinalcenterline 102. Further, the turbine section 100 includes a turbine 104,with the turbine 104 of the turbine section 100 being rotatable aboutthe axial direction A (i.e., includes one or more components rotatableabout the axial direction A). For example, in certain embodiments, theturbine 104 may be a low pressure turbine (such as the exemplary lowpressure turbine 30 of FIG. 1), or alternatively may be any otherturbine (such as, a high pressure turbine, an intermediate turbine, adual use turbine functioning as part of a high pressure turbine and/or alow pressure turbine, etc.).

Moreover, for the exemplary embodiment depicted, the turbine 104includes a plurality of turbine rotor blades spaced along the axialdirection A. More specifically, for the exemplary embodiment depicted,the turbine 104 includes a first plurality of turbine rotor blades 106and a second plurality of turbine rotor blades 108. As will be discussedin greater detail below, the first plurality of turbine rotor blades 106and second plurality of turbine rotor blades 108 are alternatinglyspaced along the axial direction A.

Referring first to the first plurality of turbine rotor blades 106, eachof the first plurality of turbine rotor blades 106 extends generallyalong the radial direction R between a radially inner end 110 and aradially outer end 112. Additionally, the first plurality of turbinerotor blades 106 includes a first turbine rotor blade 106A, a secondturbine rotor blade 106B, and a third turbine rotor blade 106C, eachspaced apart from one another generally along the axial direction A. Atleast two of the first plurality of turbine rotor blades 106 are spacedfrom one another along the axial direction A and coupled to one anotherat the respective radially outer ends 112. More specifically, for theembodiment depicted, each of the first turbine rotor blade 106A, thesecond turbine rotor blade 106B, and the third turbine rotor blade 106Care coupled to one another through their respective radially outer ends112. More specifically, still, each of the first turbine rotor blade106A, the second turbine rotor blade 106B, and the third turbine rotorblade 106C of the first plurality of turbine rotor blades 106 arecoupled at their respective radially outer ends 112 through an outerdrum 114.

Further, the second plurality of turbine rotor blades 108, each alsoextend generally along the radial direction R between a radially innerend 118 and a radially outer end 120. Additionally, for the embodimentdepicted, the second plurality of turbine rotor blades 108 includes afirst turbine rotor blade 108A, a second turbine rotor blade 108B, and athird turbine rotor blade 108C, each spaced apart from another generallyalong the axial direction A. For the embodiment depicted, at least twoof the second plurality of turbine rotor blades 108 are spaced from oneanother along the axial direction A and coupled to one another at therespective radially inner ends 118. More specifically, for theembodiment depicted, each of the first turbine rotor blade 108A, thesecond turbine rotor blade 108B, and the third turbine rotor blade 108Cof the second plurality of turbine rotor blades 108 are coupled to oneanother through their respective radially inner ends 118. Morespecifically, still, each of the first turbine rotor blade 108A, asecond turbine rotor blade 108B, and a third turbine rotor blade 108C ofthe second plurality of turbine rotor blades 108 are coupled at theirrespective radially inner ends 118 through an inner drum 116.

It should be appreciated, however, that in other exemplary embodiments,the first plurality of turbine rotor blades 106 and/or the secondplurality of turbine rotor blades 108 may be coupled together in anyother suitable manner, and that as used herein, “coupled at the radiallyinner ends” and “coupled at the radially outer ends” refers generally toany direct or indirect coupling means or mechanism to connect therespective components. For example, in certain exemplary embodiments,the second plurality of turbine rotor blades 108 may include multiplestages of rotors (not shown) spaced along the axial direction A, withthe first turbine rotor blade 108A, the second turbine rotor blade 108B,and the third turbine rotor blade 108C coupled to the respective stagesof rotors at the respectively radially inner ends 118 through, e.g.dovetail base portions. The respective stages of rotors may, in turn, becoupled together to therefore “couple the second plurality of turbinerotor blades 108 at their respective radially inner ends 118.”

Referring still to the embodiment depicted in FIG. 2, as stated, all thefirst plurality of turbine rotor blades 106 and the second plurality ofturbine rotor blades 108 are alternatingly spaced along the axialdirection A. As used herein, the term “alternatingly spaced along theaxial direction A” refers to the second plurality of turbine rotorblades 108 including at least one turbine rotor blade positioned alongthe axial direction A between two axially spaced turbine rotor blades ofthe first plurality of turbine rotor blades 106. For example, for theembodiment depicted, alternatingly spaced along the axial direction Arefers to the second plurality of turbine rotor blades 108 including atleast one turbine rotor blade positioned between the first and secondturbine rotor blades 106A, 106B of the first plurality of turbine rotorblades 106 along the axial direction A, or between the second and thirdturbine rotor blades 106B, 106C of the first plurality of turbine rotorblades 106 along the axial direction A. More specifically, for theembodiment depicted, the first turbine rotor blade 106A of the firstplurality of turbine rotor blades 106 is positioned aft of the firstturbine rotor blade 108A of the second plurality of turbine rotor blades108; the second turbine rotor blade 106B of the first plurality ofturbine rotor blades 106 is positioned between the first and secondturbine rotor blades 108A, 108B of the second plurality of turbine rotorblades 108; and the third turbine rotor blade 106C of the firstplurality of turbine rotor blades 106 is positioned between the secondand third turbine rotor blades 108B, 108C of the second plurality ofturbine rotor blades 108.

Notably, however, in other exemplary embodiments, the first plurality ofturbine rotor blades 106 may have any other suitable configurationand/or the second plurality of turbine rotor blades 108 may have anyother suitable configuration. For example, it will be appreciated thatfor the embodiments described herein, the first turbine rotor blade106A, second turbine rotor blade 106B, and third turbine rotor blade106C of the first plurality of turbine rotor blades 106 generallyrepresent a first stage of turbine rotor blades, a second stage ofturbine rotor blades, and a third stage of turbine rotor blades,respectively. It will similarly be appreciated that the first turbinerotor blade 108A, second turbine rotor blade 108B, and third turbinerotor blade 108C of the second plurality of turbine rotor blades 108each also generally represent a first stage of turbine rotor blades, asecond stage of turbine rotor blades, and a third stage of turbine rotorblades, respectively. Notably, it will be appreciated that the terms“first,” “second,” and “third” are used herein simply to distinguishcomponents and that in other embodiments the components may have anyother suitable name (e.g., in other embodiments, the third stage ofturbine rotor blades represented by blade 108C, may be referred to asthe “first stage” of turbine rotor blades of the turbine 104, the thirdstage of turbine rotor blades represented by blade 106C may be referredto as the “second stage” of turbine rotor blades of the turbine 104,etc.). In other exemplary embodiments, the first plurality of turbinerotor blades 106 and/or the second plurality of turbine rotor blades 108may include any other suitable number of stages of turbine rotor blades,such as two stages, four stages, etc., and further that in certainexemplary embodiments, the turbine 104 may additionally include one ormore stages of non-rotating stator vanes.

Referring still to the embodiment of FIG. 2, the turbine 104 furtherdefines a midpoint 176 along the axial direction A. As used herein, theterm “midpoint” refers generally to an axial location halfway between aforward-most forward edge of a forward-most turbine rotor blade of theturbine 104 and an aft-most aft edge of an aft-most turbine rotor bladeof the turbine 104. Accordingly, for the embodiment depicted, themidpoint 176 of the turbine 104 is an axial location halfway between aforward-most forward edge 172 of the third turbine rotor blade 108C ofthe second plurality of turbine rotor blades 108 and an aft-most aftedge 174 of the first turbine rotor blade 106A of the first plurality ofturbine rotor blades 106.

Moreover, for the embodiment depicted, the turbomachine further includesa gearbox 122 and a spool 124, with the first plurality of turbine rotorblades 106 and the second plurality of turbine rotor blades 108rotatable with one another through the gearbox 122. In at least certainexemplary embodiments, the spool 124 may be configured as, e.g., theexemplary low pressure spool 36 described above with reference toFIG. 1. Additionally, the exemplary turbine section further includes aturbine center frame 150 and a turbine rear frame 152. The gearbox 122is aligned with, or positioned forward of, the midpoint 176 of theturbine 104 and, for the embodiment depicted, the gearbox 122 is furtheraligned with or positioned aft of the turbine center frame 150. Morespecifically, for the embodiment depicted, the gearbox 122 is positionedforward of the midpoint 176 of the turbine 104 and aft of the turbinecenter frame 150. Notably, as used herein, the term “aligned with,” withreference to the axial direction A, refers to the two components and/orpositions having at least a portion of the same axial position.

It should be appreciated, however, that in other exemplary embodiments,the spool 124 may be any other spool (e.g., a high pressure spool, anintermediate spool, etc.), and further that the gearbox 122 may be anyother suitable speed change device positioned at any other suitablelocation. For example, in other exemplary embodiments, the gearbox 122may instead be a hydraulic torque converter, an electric machine, atransmission, etc., and may be aligned with, or positioned aft of, theturbine center frame 150, or further still may be positioned forward ofthe turbine center frame 150.

Referring still to FIG. 2, the turbine section 100 includes a firstsupport member assembly 126 having a first support member 128, and asecond support member assembly 132 having a second support member 134.The first support member 128 couples the radially inner end 110 of thefirst turbine rotor blade 106A of the first plurality of turbine rotorblades 106 to the spool 124, and further couples the first plurality ofturbine rotor blades 106 to the gearbox 122. Additionally, the secondsupport member 134 similarly couples the second plurality of turbinerotor blades 108, or rather the radially inner end 118 of the firstturbine rotor blade 108A of the second plurality of turbine rotor blades108, to the gearbox 122. Moreover, the spool 124 includes an extension130 coupling the spool 124 to the gearbox 122, the extension 130 locatedforward of the gearbox 122.

Further, for the embodiment depicted the extension 130 includes a firstflexible connection 138 attached to, or formed integrally with theextension 130. Similarly, the second support member assembly 132includes a second flexible connection 142 attached to, or formedintegrally with, the second support member 134. The first flexibleconnection 138 and second flexible connection 142 allow for a less rigidconnection between the gearbox 122 and the extension 130 and secondsupport member 134, respectively. More particularly, the first flexibleconnection 138 and the second flexible connection 142 allow for a lessrigid connection between the gearbox 122 and the first plurality ofturbine rotor blades 106 and the second plurality of turbine rotorblades 108, respectively. In certain embodiments, the first flexibleconnection 138, the second flexible connection 142, or both, may beconfigured as members having bellows, splined connections with resilientmaterial, etc.

Referring still to FIG. 2, the exemplary gearbox 122 depicted generallyincludes a first gear coupled to the first plurality of turbine rotorblades 106, a second gear coupled to the second plurality of turbinerotor blades 108, and a third gear coupled to the turbine center frame150. More specifically, for the embodiment depicted, the gearbox 122 isconfigured as a planetary gearbox, and more specifically, still, firstgear is a ring gear 144, the second gear is a sun gear 148, and thethird gear is a planet gear 146 (or rather a plurality of planet gears146 coupled to a plane gear carrier, not shown). Further, for theexemplary embodiment depicted, the turbine section 100 further includesa center frame support assembly 154 coupled to the turbine center frame150, and a rear frame support assembly 156 coupled to the turbine rearframe 152. The center frame support assembly 154, for the embodimentdepicted, includes a radially inner center frame support member 158 anda radially outer center frame support member 160. The plurality ofplanet gears 146 (or planet gear carrier, not shown) are fixedly coupledto the turbine center frame 150 through the center frame supportassembly 154, and more particularly, through the radially outer centerframe support member 160 of the center frame support assembly 154.

In such a manner, it will be appreciated that for the embodimentdepicted the first plurality of turbine rotor blades 106 are configuredto rotate in an opposite direction than the second plurality of turbinerotor blades 108. For example, the first plurality of turbine rotorblades 106 may be configured to rotate in a first circumferentialdirection C1 (see FIG. 4, below), while the second plurality of turbinerotor blades 108 may be configured to rotate in a second circumferentialdirection C2 (see FIG. 4, below), opposite the first circumferentialdirection C1.

It should further be understood that the first circumferential directionC1 and the second circumferential direction C2 as used and describedherein are intended to denote directions relative to one another.Therefore, the first circumferential direction C1 may refer to aclockwise rotation (viewed from downstream looking upstream) and thesecond circumferential direction C2 may refer to a counter-clockwiserotation (viewed from downstream looking upstream). Alternatively, thefirst circumferential direction C1 may refer to a counter-clockwiserotation (viewed from downstream looking upstream) and the secondcircumferential direction C2 may refer to a clockwise rotation (viewedfrom downstream looking upstream).

It will further be appreciated that for the embodiment depicted, thefirst plurality of turbine rotor blades 106 is configured as a pluralityof low-speed turbine rotor blades, while the second plurality of turbinerotor blades 108 is configured as a plurality of high-speed turbinerotor blades. Such may be due to the gearing of the gearbox 122 and thefact that the first plurality of turbine rotor blades 106 are directlyrotatable with the spool 124 (which may limit a rotational speed of thefirst plurality of turbine rotor blades 106). Regardless, it will beappreciated that in such an exemplary embodiment, the first supportmember 128 of the first support member assembly 126 is a low-speedsupport member, and further, the second support member of the secondsupport member assembly is a high-speed support member. Morespecifically, with such an exemplary embodiment the first plurality ofturbine rotor blades 106 is coupled to the first gear, i.e., the ringgear 144, of the gearbox 122 through the spool 124, and morespecifically, through the low-speed support member (i.e., the firstsupport member 128), the spool 124, and the extension 130. Further, withsuch an exemplary embodiment the second plurality of turbine rotorblades 108 is coupled to the second gear, i.e., the sun gear 148, of thegearbox 122 through the high-speed support member (i.e., the secondsupport member 134).

Moreover, the turbomachine includes a bearing assembly 162 to supportthe various rotating components of the turbine 104 described herein andfurther to support the spool 124 within the turbine section 100. For theembodiment depicted, the bearing assembly 162 includes a first bearing164 and a second bearing 166 supporting the spool 124 within the turbinesection 100. The first bearing 164 is positioned forward of the gearbox122 and supported by the turbine center frame 150 and the second bearing166 is positioned aft of the gearbox 122 and supported by the turbinerear frame 152. More specifically, for the embodiment depicted, thesecond bearing 166 is positioned aft of where the first support member128 (i.e., the low-speed support member for the embodiment depicted)meets the spool 124, and is supported by the turbine rear frame 152through the rear frame support assembly 156.

Further, for the embodiment depicted, the second plurality of turbinerotor blades 108, and more particularly, the second support member 134(i.e., the high-speed support member for the embodiment depicted), issupported by a bearing of the bearing assembly 162 located aft of thegearbox 122. More specifically, the exemplary bearing assembly 162depicted further includes a third bearing 168 and a fourth bearing 170,with the third bearing 168 and the fourth bearing 170 supporting thesecond support member 134 at a location aft of the gearbox 122. As isdepicted, the third bearing 168 and the fourth bearing 170 are, for theembodiment of FIG. 2, each configured as inter-shaft bearings positionedbetween the spool 124 and the second support member 134. Moreparticularly, for the embodiment depicted, the third bearing 168 and thefourth bearing 170 each support the spool 124 at a radially inner side(not labeled) and each support the high-speed support member at aradially outer side (not labeled).

Notably, for the embodiment depicted, the first bearing 164, the secondbearing 166, and the third bearing 168 are each configured as a rollerbearing and the fourth bearing 170 is configured as a ball bearing.However, in other exemplary embodiments, one or more of these bearingsmay be configured in any other suitable manner, such as the other of aroller bearing or ball bearings, a tapered roller bearing, an airbearing, etc.

Inclusion of a gearbox of a turbomachine in accordance with the presentdisclosure at a forward location relative to a midpoint of a turbine maymaintain the gearbox forward of a center of mass of the turbine, whichmay minimize vibrations of certain components, e.g., within the turbinesection. Further, such may allow additional room for a bearing assemblyto include one or more bearings positioned closer along an axialdirection to the center of mass of the turbine, with at least two ofsuch bearings straddling the midpoint of the turbine. Further, for theembodiments including one or more inter-shaft bearings, such bearingsmay assist with maintaining clearances within the turbine, as suchinter-shaft bearings may allow for any movement or deflection of a firstplurality of turbine rotor blades to coincide with a movement ordeflection of a second plurality of turbine rotor blades (e.g., duringmaneuvers of an aircraft including the turbomachine).

It should further be appreciated that in other exemplary embodiments,the turbine section 100 may have any other suitable configuration forsupporting the first plurality of turbine rotor blades 106 and thesecond plurality of turbine rotor blades 108. For example, referring nowto FIG. 3, a turbine section 100 including a turbine 104 in accordancewith another exemplary embodiment of the present disclosure is depicted.The exemplary turbine section 100 and turbine 104 depicted in FIG. 3 maybe configured in substantially the same manner as exemplary turbinesection 100 and turbine 104 of FIG. 2, and accordingly, the same orsimilar numbers refer to the same or similar parts.

For example, the exemplary turbine 104 of FIG. 3 generally includes afirst plurality of turbine rotor blades 106 and a second plurality ofturbine rotor blades 108, the first plurality of turbine rotor blades106 and second plurality of turbine rotor blades 108 alternatinglyspaced along the axial direction A. The first plurality of turbine rotorblades 106 is rotatable with the second plurality of turbine rotorblades 108 through a gearbox 122. More particularly, the first pluralityof turbine rotor blades 106 is mechanically coupled to a first gear ofthe gearbox 122 through a first support member 128 (which may be alow-speed support member for the embodiment depicted) and a spool 124.Additionally, the second plurality of turbine rotor blades 108 ismechanically coupled to a second gear of the gearbox 122 through asecond support member 134 (which may be a high-speed support member forthe embodiment depicted).

A bearing assembly 162 is provided to rotatably support rotation of theturbine 104 (and more specifically, the second support member assembly132) and the spool 124 within the turbine section 100. The exemplarybearing assembly 162 generally includes a first bearing 164 and a secondbearing 166 rotatably supporting the spool 124, with the first bearing164 supported by a turbine center frame 150 through a radially innercenter frame support member 158 (of a center frame support assembly 154)and the second bearing 166 supported by a turbine rear frame 152 througha rear frame support assembly 156. The bearing assembly 162 additionallyincludes a third bearing 168 and a fourth bearing 170.

The third bearing 168 and the fourth bearing 170 are configured tosupport rotation of the second plurality of turbine rotor blades 108(i.e., through, for the embodiment depicted, the second support member134 for the embodiment depicted). However, for the embodiment of FIG. 3,the third bearing 168 and the fourth bearing 170 are not configured asinter-shaft bearings, and instead are hard mounted. More particularly,the third bearing 168 and fourth bearing 170 are supported by theturbine center frame 150 through a radially outer center frame supportmember 160 of the center frame support assembly 154. Positioning thethird bearing 168 and fourth bearing 170 at the radially outer location,supported by the turbine center frame 150 may provide more robustsupport for the second plurality of turbine rotor blades 108.

It will be appreciated, that in other exemplary embodiments, the turbine104, and the turbomachine in general, may have any other suitableconfiguration. For example, in other exemplary embodiments, the gearbox122 may be aligned with the midpoint 176 of the turbine 104, may bealigned with the turbine center frame 150, or may be positioned forwardof the turbine center frame 150. Additionally, although the exemplarybearing assembly 162 depicted in FIGS. 2 and 3 includes a total of fourbearings, in other exemplary embodiments, the bearing assembly 162 mayinstead include three bearings, two bearings, five bearings, or anyother suitable number of bearings. For example, in other exemplaryembodiments, the third bearing 168 and the fourth bearing 170 of thebearing assembly 162 may be configured as a single bearing.

It will further be appreciated that in at least certain exemplaryembodiments, the first plurality of turbine rotor blades 106 and thesecond plurality of turbine rotor blades 108 may have any other suitableconfiguration. For example, in other exemplary embodiments, the firstand/or second pluralities of turbine rotor blades 106, 108 may beconfigured in a split drum configuration. More specifically, in certainalternative exemplary embodiments, the first plurality of turbine rotorblades 106 may include a first turbine rotor blade 106A, a secondturbine rotor blade 106B, and a third turbine rotor blade 106C spacedalong an axial direction A. A radially outer end 112 of the firstturbine rotor blade 106A may be coupled to a radially outer end 112 ofthe second turbine rotor blade 106B, and a radially inner end 110 of thesecond turbine rotor blade 106B may be coupled to a radially inner end110 of the third turbine rotor blade 106C. For example, the firstturbine rotor blade 106A and second turbine rotor blade 106B of thefirst plurality of turbine rotor blades 106 may be coupled through afirst outer drum, and further the second turbine rotor blade 106B andthe third turbine rotor blade 106C of the first plurality of turbinerotor blades 106 may be coupled through a first inner drum.

Further, in certain of these alternative exemplary embodiments, thesecond plurality of turbine rotor blades 108 may similarly include afirst turbine rotor blade 108A, a second turbine rotor blade 108B, and athird turbine rotor blade 108C spaced along an axial direction A, andmore particularly, alternatingly spaced along the axial direction A withthe first plurality of turbine rotor blades 106. A radially inner end118 of the first turbine rotor blade 108A may be coupled to a radiallyinner end 118 of the second turbine rotor blade 108B, and further, aradially outer end 120 of the second turbine rotor blade 108B may becoupled to the radially outer end 120 of the third turbine rotor blade108C. More specifically, the first turbine rotor blade 108A and secondturbine rotor blade 108B may be coupled through a second inner drum 117,and the second turbine rotor blade 108B and the third turbine rotorblade 108C may be coupled through a second outer drum 115. Otherconfigurations are contemplated as well.

Referring now to FIG. 4, an exemplary embodiment of an orientation ofthe first plurality of turbine rotor blades 106 and the second pluralityof turbine rotor blades 108 is generally provided. The first pluralityof turbine rotor blades 106 and the second plurality of turbine rotorblades 108 may be the same rotor blades discussed above with referenceto, e.g., FIGS. 2 and 3.

More specifically, the embodiment of FIG. 4 depicts a first stage ofturbine rotor blades 106A of the first plurality of turbine rotor blades106 and a first stage of turbine rotor blades 108A of the secondplurality of turbine rotor blades 108. In at least certain exemplaryembodiments, the first plurality of turbine rotor blades may beconfigured to rotate in a first circumferential direction C1, while thesecond plurality of turbine rotor blades may be configured to rotate ina second circumferential direction C2.

It will be appreciated that for the embodiment depicted, each of theturbine rotor blades 106A of the first plurality of turbine rotor blades106 include an airfoil 180, and similarly, each of the turbine rotorblades 108A of the second plurality of turbine rotor blades 108 includean airfoil 182. The airfoils 180 each define an exit angle 184, andsimilarly the airfoils 182 each define an exit angle 186. The exitangles 184, 186 each represent an angular relationship of a longitudinalcenterline 102 (i.e., of the turbomachine within which they areinstalled) to an exit direction of the gases flowing from an upstreamend 188 towards a downstream end 190 of the respective airfoils 180,182. For the embodiment depicted, the exit angle 184 may be a negativeangle, such as a negative acute angle, while the exit angle 186 may be apositive angle, such as a positive acute angle (“positive” and“negative” being used herein to denote a relative value of therespective exit angles 184, 186 viewed from the same perspective).Notably, the exit angles 184, 186 of the airfoils 180, 182,respectively, a cause the first plurality of turbine rotor blades 106and second plurality of turbine rotor blades 108 to rotate in the firstand second circumferential directions C1, C2, respectively.

Referring still to FIG. 4, the airfoils 180, 182 may each furtherinclude a suction side 192 and a pressure side 194. The suction side 192of the airfoils 180 are configured as convex toward the firstcircumferential direction C1 and the pressure side 194 of the airfoils180 are configured as concave toward the first circumferential directionC1. The suction side 192 of the airfoils 182 are configured as convextoward the second circumferential direction C2 and the pressure side 194of the airfoils 180 are configured as concave toward the secondcircumferential direction C2. Such a configuration may further result inthe first plurality of turbine rotor blades 106 and second plurality ofturbine rotor blades 108 rotating in the first and secondcircumferential directions C1, C2, respectively.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A turbomachine defining a radial direction and anaxial direction, the turbomachine comprising: a turbine sectioncomprising a turbine center frame and a turbine, the turbine defining amidpoint along the axial direction and comprising a plurality oflow-speed turbine rotor blades and a plurality of high-speed turbinerotor blades, the plurality of low-speed turbine rotor blades andplurality of high-speed turbine rotor blades alternatingly spaced alongthe axial direction, the plurality of low-speed turbine rotor bladeseach extending between a radially inner end and a radially outer end,wherein at least two of the plurality of low-speed turbine rotor bladesare spaced from one another along the axial direction and coupled to oneanother at the radially outer ends; and a gearbox aligned with, orpositioned forward of, the midpoint of the turbine, the gearboxcomprising a first gear coupled to the plurality of low-speed turbinerotor blades, a second gear coupled to the plurality of high-speedturbine rotor blades, and a third gear coupled to the turbine centerframe.
 2. The turbomachine of claim 1, wherein the gearbox is positionedforward of the midpoint of the turbine.
 3. The turbomachine of claim 1,wherein the first gear of the gearbox is a ring gear, and wherein thesecond gear of the gearbox is a sun gear.
 4. The turbomachine of claim1, wherein each of the plurality of low-speed turbine rotor blades arecoupled to one another at the radially outer ends.
 5. The turbomachineof claim 1, wherein the plurality of high-speed turbine rotor bladeseach extend between a radially inner end and a radially outer end, andwherein at least two of the plurality of high-speed turbine rotor bladesare spaced from one another along the axial direction and coupled to oneanother at the radially inner ends.
 6. The turbomachine of claim 5,wherein each of the plurality of high-speed turbine rotor blades arecoupled to one another at the radially inner ends.
 7. The turbomachineof claim 1, further comprising: a turbine rear frame; and a spool,wherein plurality of low-speed turbine rotor blades is coupled to thefirst gear of the gearbox through the spool, wherein the spool isrotatably supported by a first bearing and a second bearing, wherein thefirst bearing is positioned forward of the gearbox and supported by theturbine center frame, and wherein the second bearing is positioned aftof the gearbox and supported by the turbine rear frame.
 8. Theturbomachine of claim 1, further comprising: a high-speed supportmember, wherein the plurality of high-speed turbine rotor blades arecoupled to the second gear through the high-speed support member.
 9. Theturbomachine of claim 8, wherein the high-speed support member isrotatably supported by a bearing located aft of the gearbox.
 10. Theturbomachine of claim 9, wherein the bearing is supported by the turbinecenter frame.
 11. The turbomachine of claim 9, further comprising: aspool, wherein the plurality of low-speed turbine rotor blades iscoupled to the first gear of the gearbox through the spool, and whereinthe bearing is an inter-shaft bearing positioned between the spool andthe high-speed support member.
 12. The turbomachine of claim 11, whereinthe inter-shaft bearing supports the spool at a radially inner side, andwherein the inner shaft bearing supports the high-speed support memberat a radially outer side.
 13. The turbomachine of claim 8, wherein thehigh-speed support member is rotatably supported by a plurality ofbearings located aft of the gearbox.
 14. The turbomachine of claim 1,wherein the gearbox is aligned with, or positioned aft of, the turbinecenter frame.
 15. The turbomachine of claim 1, wherein the plurality ofhigh-speed turbine rotor blades is coupled to the second gear of thegearbox through a flexible member, and wherein the turbomachinecomprises: a spool, wherein plurality of low-speed turbine rotor bladesis coupled to the first gear of the gearbox through the spool, andwherein the spool is connected to the first gear through a flexiblemember.
 16. A turbomachine defining a radial direction and an axialdirection, the turbomachine comprising: a spool; a turbine sectioncomprising a turbine center frame, a turbine rear frame, and a turbine,the turbine comprising a first plurality of turbine rotor blades and asecond plurality of turbine rotor blades, the first plurality of turbinerotor blades and second plurality of turbine rotor blades alternatinglyspaced along the axial direction, the turbine defining a midpoint alongthe axial direction; a gearbox aligned with, or positioned forward of,the midpoint of the turbine, the gearbox comprising a first gear coupledto the first plurality of rotor blades through the spool, a second gearcoupled to the second plurality of rotor blades, and a third gearcoupled to the turbine center frame; and a bearing assembly comprising abearing supporting spool and located aft of the gearbox, the bearingsupported by the turbine rear frame.
 17. The turbomachine of claim 16,wherein the gearbox is positioned forward of the midpoint of theturbine, and aligned with, or positioned aft of, the turbine centerframe.
 18. The turbomachine of claim 16, wherein the first plurality ofturbine rotor blades is a plurality of low-speed turbine rotor blades,wherein the second plurality of turbine rotor blades is a plurality ofhigh-speed turbine rotor blades.
 19. The turbomachine of claim 18,wherein the first gear of the gearbox is a ring gear, and wherein thesecond gear of the gearbox is a sun gear.
 20. The turbomachine of claim18, wherein the plurality of low-speed turbine rotor blades each extendbetween a radially inner end and a radially outer end, and wherein atleast two of the plurality of low-speed turbine rotor blades are spacedfrom one another along the axial direction and coupled to one another atthe radially outer ends.